You need to have your ISP add an A record for your email server. I'll assume it's exchserver (I'd prefer the name mail, but it's up to you)
Your MX record should look like:
MX IN 1800 exchserver.tdcb.com

Featured Post

Are you using Office 365? Trying to set up email signatures but you’re struggling with transport rules and connectors? Let renowned Microsoft MVP J.Peter Bruzzese show you how in this exclusive e-book on Office 365 email signatures. Better yet, it’s free!

To show how to generate a certificate request in Exchange 2013. We show this process by using the Exchange Admin Center.
Log into Exchange Admin Center.: First we need to log into the Exchange Admin Center.
Navigate to the Servers >> Certificates…